1. Field of the Invention
This invention relates to a magnetic head device in which magnetic heads are slidably brought into contact with a flexible disc to read data from the disc or write data into the disc, and more particularly a magnetic head device in which the disc can be held stably by an upper magnetic head and a lower magnetic head.
2. Description of the Related Art
FIG. 7 is a side view for showing a magnetic head device 50 of the prior art.
The magnetic head device 50 shown in FIG. 7 is used in a low capacity type floppy disc device and as medium in this case a flexible disc is used.
In the aforesaid magnetic disc device 50 shown in FIG. 7, a supporting member 52 is arranged on a chassis 51. The aforesaid supporting member 52 is inserted into and guided by a guide shaft (not shown) which is arranged to face toward a radial direction of a disc D. There is also provided a driving section not shown, the supporting member 52 is guided on the guide shaft under a driving force of the driving section and moved toward a radial direction of the disc D.
A fixed arm 53 extending from the bottom part of the supporting member 52 toward the disc D is integrally formed with the supporting member 52, the fixed arm 53 can be slid at the lower surface side of the disc D, and there is provided a magnetic head 58 of a side 0 at an upper surface of the extremity end of the fixed arm 53.
In addition, the supporting member 52 is provided with a supporting arm 54 at a position opposite to the fixed arm 53, the base end of the supporting arm 54 is connected to a leaf spring 55 and the base end of the leaf spring 55 is fixed to the supporting member 52 by a screw 57. Further, the extremity end of the supporting arm 54 is provided with a magnetic head 59 of the side 1 at a position opposite to the magnetic head 58.
The leaf spring 55 is provided with a helical coil spring 56 at its upper part and the supporting arm 54 is always biased by the helical coil spring 56 toward the direction of the disc D. Additionally, this magnetic head device 50 is provided with a retracting mechanism (not shown) for retracting the magnetic head 59 above the disc D when the disc D is not loaded.
However, as a high density (a high volume) of the disc D was required, the disc D had to be rotated while its rotating speed was increased more than that of the prior art, resulting in that the prior art magnetic head device 50 had the following problem.
That is, in the case of the magnetic head device 50, the motion of the magnetic head 58 at the side 0 in its direction of height is restricted. Due to this fact, when the disc D is rotated at a high speed, if there is a certain difference between an access plane of the disc D and the magnetic heads 58, 59 in a direction of height, a strain may occur at the disc D by its own inertia. With such an arrangement as above, the magnetic heads 58, 59 could not follow the deformation of the disc D, resulting in that there was a possibility that a certain off-track state was produced, reading-in or writing-in of data into the disc failed or the disc D was damaged.
In view of the foregoing, the magnetic head device 60 as shown in FIG. 8 has been provided in which the magnetic head can follow against the deformation of the disc D.
The magnetic head device 60 shown in FIG. 8 is a mechanism in which each of both upper and lower magnetic heads 64, 65 at the side 0 and at the side 1 in respect to the supporting member 61 is supported by each of leaf spring arms 62, 63, respectively. In the magnetic head device 60 shown in FIG. 8, if the disc D is rotated at a high speed, it becomes possible to cause the magnetic heads 64, 65 to follow the disc D.
On the contrary, since the upper and lower magnetic heads 64, 65 are supported together by the leaf spring arms 62, 63, press contacted points of the magnetic heads 64, 65 with the disc D may easily be displaced in their positions in either upward or downward direction in respect to an installing reference position of the disc D due to an unbalanced biasing force of each of the upper and lower arms 62, 63.
When the press contacted points of the upper and lower magnetic heads 64, 65 with the disc D are displaced in an upward or downward direction in respect to the disc D, any one of the magnetic heads is forcedly brought into contact with a recording surface of the disc D, an excessive frictional force is imparted upon the recording surface of the disc D or the magnetic heads. The result is that the recording surface of the disc or the sliding surface of each of the magnetic heads may easily be damaged.
Further, the disc is also deformed, the leaf spring arms 62, 63 for supporting the magnetic heads 64, 65 under repelling force attained from the deformation may easily be deformed under a specified period, resulting in that the arms 62, 63 and the magnetic heads 64, 65 may easily generate vibration S.
In the case that an amplitude of this vibration S is high, a displacement is generated between the disc D and each of the magnetic heads 64, 65 in respect to the radial direction of the disc D (a track direction), resulting in that an off-track state may easily be produced.
In reference to the foregoing arrangement, in the case of the magnetic head device 60 above, the resilient forces of the arms 62, 63 supporting the magnetic heads 64, 65 are measured individually and it becomes necessary to select each of the arms 62, 63 and combine them in such a way that the resilient forces of the upper and lower arms 62, 63 may be well balanced and its manufacturing work becomes quite complicated.